Installation of sand drains

ABSTRACT

Methods and equipment for installing sand drains in water bearing earth; and an open ended tubular shell is lowered into the earth while allowing the water bearing earth to freely enter into the interior of the shell; a close fitting auger is used to remove the water bearing earth from the shell and then the shell is filled with sand and subsequently withdrawn from the earth thus leaving the sand to provide the desired sand drain.

[ 51 Sept. 12,1972

United States Patent Hilton et al.

....l98/213 X 4/l96l Goodrich........... .198/213 11/1969 ....6l/63 [541INSTALLATION OF SAND DRAINS 292,550 1/1884 Fairly................

2 981 403 [72] Inventors: Joseph Lawrence Hilton Oakland,

NIL; G an Incline 3,478,524 .m...

Village, Nev.; Lewis Fred Cavin,

Primary Examiner-Jacob Shapiro San Lorenzo, Calif.

[73] Assignee: Raymond lntemational lnc.,

Attorney-Ward, McElhannon, Brooks & Fitzpatrick, Joseph M. Fitzpatrick,Charles B. Cannon, Carrol G.

New

York, NY.

July 20, 1970 [21] Appl. No.: 63,968

[22] Filed:

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m mmmm wm efl mem num fmw mw Wr.um M m Mm .mkfly m I e] m m e w m 0 wueu 1 m m m m .mhmfi mmm m um o.moue l t fifd 1 dm lm emm m m n m l m iwm w 93 m m mm .n em m mm Mwkmsbmamd 1 32 3 33 64 l 12 2 nunwn RB 67 i885 B ,139 97 5 2 ll 1 .d 1 3% m m UE U l l l n /6 m n" nLm m m [11 e m uU w mm 6.0 .7 A u 2 1 l P Han c t r wE3 m m a a 6 Y. my MUN m A M m m "h"r m R D m n 99 m mww L f o m d 5 3. mm U .mm 35 m m m mm l 37 U 5.5 r 22 PATENTED SE? 12 I972 SHEET 1 OF 2 INSTALLATION OF SAND DRAINS Thisinvention relates to methods and equipment for installing sand drainsand, more particularly, to methods and equipment for installingnondisplacement sand drains.

While the several aspects of the present invention are subject to a widerange of applications, they are especially suited for use in theinstallation of sand drains in water bearing earth comprised of arelatively firm surface earth and a softer-underearth, and will beparticularly described in that connection.

Sand drains are regions of high water permeability placed artificiallyin the earth and connected to a region of minimum fluid pressure such asthe atmosphere. Essentially, sand drains function to permit relativelyrapid water pressure release from locations in the earth where excesswater pressures have developed due to'construction operations. Excesswater pressures in the ground can be built up as a result of theplacement of heavy structures or earth fills on the ground, or thedriving of pilings into the ground. Because of high excess waterpressures, the stability of such structures in earth fills may be poor.Furthermore, such structures and earth fills will incur settlements withtime as the excess water pressure is gradually dissipated at a rate de-I close to these water pressure concentrations it is possible to obtaindissipation of the water pressure effects within a very short time sothat a stable condition may be achieved before further construction isundertaken.

Generally, sand drains are constructed by forming a vertical hole in theearth and filling the hole with sand or other moisture permeablematerial. Actually, it is the hole itself, which is open to the groundsurface, that achieves the moisture equalization effects. The sand orother moisture permeable substance, however, is needed to maintain andto structurally reinforce the vertical hole while at the same timeallowing relatively free flow of water to the surface.

The formation of the vertical hole and the placement of sand or othermoisture permeable material in silty earths pose especially difficultproblems. These earths are typically comprised of a relatively firmsurface earth sometimes formed from earth fills, and a softer silty ormuddy underearth, the relatively firm surface earth extending, forexample, l20 feet below the ground surface and the muddy underearthextending 7-80 feet below the ground surface. Experience has shown thatgenerally known hole forming methods are ineffective in these mentionedwater bearing earths. The commonly utilized method of predrilling a holeto the required depth and filling same with sand or other moisturepermeable material has been found unworkable since lower muddy earth issqueezed into the drilled hole and closes it off before the sand orother material can be properly positioned therein. The use of knownpre-excavator methods have also been found unworkable. The lattermethods commonly use an outer open ended shell which encloses and housesan open ended inner shell. Usually, the outer shell and the enclosedinner shell are lowered by known driving methods to the required depthwhile allowing the water bearing earth to freely enter up into theinterior of the inner shell. The inner shell containing the waterbearing earth is then extracted from the outer shell by air pressure,leaving the outer shell in the ground. The outer shellis then filledwith sand and thereafter is also withdrawn from the earth, thus leavingthe sand to provide the desired sand drain. ln driving the inner andouter shells, however, the relatively firm surface earth forms a plug inthe inner shell thus causing, in a well known manner, some detrimentallateral displacement of the earth surrounding the hole. In addition, inextracting the inner shell from the outer shell, a vacuum is createdbeneath the lower end of the inner shell, thus pulling the water bearingearth into the hole defined by A the outer shell.

The present invention overcomes the abovedescribed difficulties andpermits the installation of effective and reliable sand drains withminimum effort and without substantial soil displacement.

According to one aspect of the present invention, a sand drain isconstructed by lowering into the water bearing earth an open ended shellwhile allowing the water bearing earth to enter freely up into theinterior of the shell through the shells lower end. The earth, which hasentered into the shell through the lower end, is then removed, whilemaintaining the shell in the ground. Thereafter, sand is introduced intothe interior of the shell, and then the shell is withdrawn from theground, leaving the sand'to provide the desired sand drain.

As hereinafter described in detail, the present invention may be carriedout by lowering an open ended tubular shell defined by joined upper andlower sections into the water bearing earth to a depth substantiallycorresponding to the length of the lower section, while allowing thewater bearing earth to enter freely up into the lower section throughits lower end. The upper section of the shell is then removed from thelower section, the latter remaining positioned in the earth. A closefitting auger is then placed within the lower section and utilized toremove from the lower section the earth which is inside. The auger isthen removed from the lower section, and the upper section of the shellrepositioned and joined to the lower section. Thereafter, sand isintroduced into the shell via the upper section and the shell, includingboth the upper and lower sections, is withdrawn from the earth, whileleaving the sand in the earth to provide the desired sand drain.

In accordance with another aspect of the present invention, air isprovided beneath the lower end of the auger during its removal from theshell so as to prevent the undesirable buildup of a vacuum which couldcause the surrounding water bearing earth to be drawn into the holedefined by the shell. in addition, the upper and lower sections of theshell are constructed to be joined together by a substantially air-tightseal. This construction enables the pressurization of the shell whenwithdrawing same from the earth, thus positioning the sand in the holewhile the shell is being removed.

According to a further aspect of the present invention, there isprovided novel sand drain formation equipment comprising a shell whichserves to form the sand drain hole, as well as an auger which serves toremove the water bearing earth from the shell. The shell is comprised ofhollow cylindrical tubing having first and second sections. Thementioned first and second sections are constructed to be mechanicallyjoined together. The firstsection is of a length equal to substantiallythe depth of the sand drain to be installed,

and has open upper and lower ends; the second section has a closed upperend and has sand input means defined therein. The auger may be comprisedof a stem portion and helical flights positioned about the stem portion.ln addition, the flights of the auger are provided with flexible'edgesfor making sealing engagement with the interior surface of the shell.

, Therehas thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the. artmay be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception upon which thisdisclosure isbased may readily be utilized as a basis for thedesigning'of other structures for carrying out the several purposes ofthe invention. It is important, therefore, that thevclaims be regardedas including such equivalent constructions as do not depart from thespirit and scope of the invention. I

Speciflcembodiments of the invention have been chosen for purposes ofillustration and description, and

are shown inthe accompanying drawings forming a part of thespecification wherein:

FIGS.-:l-7 are side elevational views, mostly in section, showing insequence, the several steps undertaken in the installation of asand-drain according to the present invention;

FIG. 8 is an enlarged elevational view, taken in section, of an augerconstructed in accordance with the presentinvention and used in thesequence of steps illustr ated in FIG 1-, '--7; I

FIG. 9 is a side evationalview, taken in section, of a {shell constructaccordance with the present invention and also sed n the sequence ofsteps illustrated in FIG. 1;and, I

' FIG. l0is a .l0ofFlG.9.

In FIGS. l--j7, -'the re is shown a mass of saturated water bearing ea'rkthf-l-8which, in the usualsituation, may extend dowrito aconsiderable depth below the surface, for le from 60 to 80 feet, beforereaching afi e320 of solid earth or rock. As also somewhat sch ianyshown in FIG. 1, the water ay ,corjtipris'e a relatively firm surface rbrmuddy underearth 24, the relafta'gmentary view taken along line 10-surface.

In accordan shown in FIG the relatively x underearth 24, The'j workinghole 26 may be provided by any knownfimeth'iod, such as drilling with anauger, jetting etc. As will become more apparent hereafter, theprovision'of the working hole 26 prevents the buildup of a plug"? ithinhollow equipment subsequently placed in the earth.'- P I As shown inFIGZ an open ended tubular shell 28 having joined upper and lower sections30 and 32 respectively, is lowered into the water bearing earth 18through the working hole 26 to a depthsubstantially corresponding to thelength of the lower section 32. The structural details of the shell 28will be more fully described hereinafter. As those skilled in the artwill appreciate, the shell 28 may be lowered by any known means, such asby a vibrator or driving hammer (not shown). During the loweringoperation, the softer underearth 24 freely enters up intothe interior ofthe shell 28 through the open bottom end of the shell's lower section32. After the shell 28 has been positioned as described above, the uppersection 30 isthen removed to provide free access and working room on theground about the lower section 32.

As shown in FIG. 3, the underearth 24 which has entered up into theshell 28 through the lower end of lower section 32 is then removed. Tothis end, a close fitting auger 34 is placed within the lower section 32and passed therethrough to removethe water bearing earth. As shown inFIG. 8, the auger 34 may be comprised of a stem portion 36 having aninternal channel 38 and helical flights 40. The internal channel 38extends through the stem portion 36 and opens out through an aperture 42(FIG. 1) in the tip of the auger 34. In addition, a strip of belting 44(FIG. 8) is secured on the edges of the flights 40 of the auger 34 bysuitable fastening means, such as a plate 46. It;will be appreciatedthat the auger 34 is thus provided with flexible edges which makesealing engagement with the lower portion 32 of the shell 28 (FIG. 3),and which facilitate inthe removal of the underearth 24 within. Asschematically shown by the arrows 48 in FIG. 3, compressed air issupplied from an external source (not shown) and is introduced at groundlevel through the internal channel 38 of the auger 34, and appliedbeneath the lower tip of the auger 34. The application of this airwithin the lower -section 32 of the shell prevents the buildup of avacuurrrwhen the'auger 34 is removed, and thus'prevents th pulling ofsurrounding water bearing earth into the hole defined by the shell.

Depending on the consistency of the water bearing earth which hasentered up into the-lower section 32, it may be necessary to make aplurality of passes with-the auger 34 in order to completely remove thewater bearing earth. FIG. 4 shows the lower section 32 of a shell havingthe water bearing earthfjcompletely removed therefrom. Y y i 't a Afterthe water bearing earthwhich had entered 'up into the lower section 32of the shell has been removed, the upper section 30 is repositioned andsecured to the lower section 32 as sho'wninFlG. SJAt' this point, sand50 is introduced into the shell 28fvia the upper section 30 tosubstantially fill at least the lower section 32. As shown, the sand '50is poured from a sand skip 52 into the shell 28 through a sand inputS4formed near the upper end of the upper section 30..As shown in FIG.'1, the sand input 54 is provided with an air-tight door 56 mounted on apivot 58,

Thereafter, as shown in FIG. 6, the door 54 is closed and pressurizedair is admitted to the interior of the shell28 via an air connection 60also located near the top of the shell 28. The applied pressurized airfacilitates the removal of the shell 28 while at the same time properlypositioning the sand inthe thus formed hole. Simultaneously, the shell28 is withdrawn from the water bearing earth 18 while leaving the sand50 to provide a completed sand drain. The thus completed sand drain isshown in FIG. 7.

Referring now to FIGS. 9 and 10, there is shown in greater detail theshell 28 used in connection with the installation of sand drains inaccordance with the present invention. As aforesaid, the shell 28 iscomprised of upper and lower sections 30 and 32, respectively,mechanically joined together; the lower section 32 being of a lengthsubstantially equal to the depth of the sand drain to be installed andhaving an open outer end (not shown). The lower section 32 also has aflange or collar 62 which forms a seat for the upper section 30. A tenon64, having an outer diameter slightly smaller than the internal diameterof the lower section 32, is provided on the upper section 30 in order toengage and extend into the lower section 32. As shown in FIG. 10,pulling hooks 66 are provided on the upper section 32 in order toprovide suitable means for pulling the shell 28 from the ground. Liftinghooks 68 are also provided-on the upper section 30 by means of pad eyes"70 or the like. The hooks 68 extend down to and are secured by latches72 provided beneath the flange 62 of the lower section 32. The liftinghooks 68 function to transmit to the lower section 32 the pulling forcesapplied to the pulling hooks 66 on the upper section 30.

In order to make the shell 28 substantially air-tight and thus increasethe effectiveness of the pressurized air applied through the airconnection 60, an O ring 74 or similar seal is provided between thetenon 64 and the lower section 32. In order to secure and hold the 0ring 74 in position during the removal and repositioning of the uppersection 30 to the lower section 32, two spaced apart metal bands 76 maybe integrally formed on the outside of the tenon 64.

Also as shown in FIGS. 9 and 10, the lower section 32 of the shell 28 isprovided with two male members 78, located opposite each other 180 aboutthe periphery of the lower section 32. The upper section 30 of the shell28 is also provided with slots shaped in complement to the male members78, and arranged on the upper section 30 so as to engage the malemembers 78. The cooperation of the male and female members 78 and 80,respectively, prevents relative rotation between the upper section 30and the lower section 32 and functions as guide means for carrying outquick hook up between the upper and lower sections.

Thus, it will be seen from the above that in accordance with the presentinvention there are provided methods and equipment for installing sanddrains without causing substantial adjacent earth displacement, andwhich permit the installation of effective and reliable sand drains.

Having thus described the invention with particular reference to thepreferred forms thereof, it will be obvious to those skilled in the artto which the invention pertains, after understanding the invention, thatvarious changes and modifications may be made therein without departingfrom the spirit and scope of the invention as defined by the claimsappended hereto.

What is claimed and desired to be secured by Letters Patent is:

1. A method for forming a hole in the earth, said meth d om risin theste s of insertin an 0 en ended tu ulai' shefi down in to the earth s othat ihe earth surrounded by the shell enters up inside it andthereafter causing an auger to bore down into the shell and removing theauger longitudinally from the shell while wiping the inner surfaces ofthe shell with flexible elements secured to the flights of the auger.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3'G9O'388Dated September 1 2J 1972 Inventor(s) Hllton: t al It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the Abstract line 2, delete the word "and";

Column 1., line 51, for "7" read --70--;

Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M FLETCHER JR ROBERT GOTTSCHALK Attest1ng Officer Commissioner ofPatents ORV. O-1050 (10-69) USCOMM-DC SO375-PE9 v.5. GOVERNMENT PR2

1. A method for forming a hole in the earth, said method comprising thesteps of inserting an open ended tubular shell down into the earth sothat the earth surrounded by the shell enters up inside it andthereafter causing an auger to bore down into the shell and removing theauger longitudinally from the shell while wiping the inner surfaces ofthe shell with flexible elements secured to the flights of the auger.